Implant delivery assembly with expandable coupling/decoupling mechanism

ABSTRACT

An occlusive implant delivery assembly includes a rapid response decoupling or detachment mechanism that does not effect significant migration of the implant during release. The assembly includes an occlusive implant device, such as an embolic coil, a pusher or device to carry the implant to the selected location, and an expandable coupling-decoupling mechanism for releasing the implant at the selected site. The mechanical construction provides rapid release times. In addition, the releasing mechanism generally operates without exerting any significant force on the implant, thereby avoiding any significant displacement of the implant during release.

RELATED PATENT APPLICATION

This application is a continuation of U.S. patent application Ser. No.09/034,606, now U.S. Pat. No. 6,238,415, filed on Mar. 3, 1998, which isa continuation of U.S. patent application Ser. No. 08/363,264, now U.S.Pat. No. 5,814,062, filed on Dec. 22, 1994.

FIELD OF THE INVENTION

The present invention generally relates to surgical instruments. Moreparticularly, the invention relates to delivery assemblies fordelivering an occlusive device, such as an embolic coil, to a selectedsite within a mammal using an expandable coupling or decouplingmechanism.

BACKGROUND OF THE INVENTION

The endovascular treatment of a variety of vascular maladies throughoutthe body is an increasingly more important form of therapy. Cathetershave been used to place various treatment materials, devices, and drugswithin arteries and veins in the human body. Examples of these devicesand their use in such treatments are shown in U.S. Pat. Nos. 5,234,437and 5,261,916, in which methods and devices for delivery of coils orwires within the human body to sites, such as aneurysms, to occludethose sites are disclosed. Coils, such as those discussed in thesedocuments as well as in U.S. Pat. No. 4,994,069, may be of a regular orhelical configuration or assume a random convoluted configuration at thesite. The coils normally are made of a radiopaque, biocompatible metalsuch as platinum, gold, tungsten or alloys of these and other metals. Intreating aneurysms, it is common to place a number of coils within theaneurysm. The coils occlude the site by posing a physical barrier toblood flow and by promoting thrombus formation at the site.

Coils have typically been placed at the desired site within thevasculature using a catheter and a pusher. The site is first accessed bythe catheter. In treating peripheral or neural conditions requiringocclusion, the sites are accessed with flexible, small diametercatheters such as those shown in U.S. Pat. Nos. 4,739,768 and 4,813,934.The catheter may be guided to the site through the use of guidewires(see U.S. Pat. No. 4,884,579) or by flow-directed means such as balloonsplaced at the distal end of the catheter. Use of guidewires involves theplacement of relatively long, torqueable proximal wire sections withinthe catheter attached to more flexible distal end wire sections designedto be advanced across sharp bends at vessel junctions. The guidewire isvisible using x-ray techniques and allows a catheter to be navigatedthrough extremely tortuous vessels, even those surrounded by soft tissuesuch as the brain.

Once the site has been reached, the catheter lumen is cleared byremoving the guidewire (if a guidewire has been used), and one or morecoils are placed into the proximal open end of the catheter and advancedthrough the catheter with a pusher. Pushers are wires having distal endsadapted to engage and push the coil through the catheter lumen as apusher itself is advanced through the catheter. Once the coil reachesthe distal end of the catheter, it is discharged from the catheter bythe pusher into the vascular site. However, there are concerns whendischarging the coil from the distal end of the catheter. For example,the plunging action of the pusher and the coil can make it difficult toposition the coil at the site in a controlled manner and with a finedegree of accuracy. Inaccurate placement of the coil can be problematicbecause once the coil has left the catheter, it is difficult toreposition or retrieve the coil.

Several techniques involving Interlocking Detachable Coils (IDCs), whichincorporate mechanical release mechanisms and Guglielmi Detachable Coils(GDCs), which utilize electrolytically actuated release mechanisms, havebeen developed to enable more accurate placement of coils within avessel.

One technique for detaching an embolic coil is shown in U.S. Pat. No.5,261,916. According to that technique, a coil having an enlargedportion is mated with a pusher having a keyway adapted to receive theenlarged portion of the coil in an interlocking relationship. The jointbetween the pusher and the coil is covered by a coaxial member. Thecoaxial member is movable by sliding the member axially. As the coaxialmember is moved away from the junction where the coil's member engagesthe keyway of the pusher, the coil is freed from the catheter assemblyand the pusher may then be removed.

Another IDC device for placement of coils is shown in U.S. Pat. No.5,234,437. This device includes a coil having a helical portion at leastone end and a pusher wire having a distal end that is threaded inside onthe helical coil by use of a threaded section on the outside of thepusher. The device operates by engaging the proximal end of the coilwith a sleeve and unthreading the pusher from the coil. Once the pusheris free, the sleeve may be used to push the coil out into the targetedtreatment area.

U.S. Pat. No. 5,312,415 discloses the use of a catheter having aconstricted or feathered end to retain a number of embolic coils on aguidewire for precise placement using a pusher sheath.

Electrolytic coil detachment is disclosed in U.S. Pat. Nos. 5,122,136and 5,354,295. As disclosed in U.S. Pat. No. 5,122,136, the coil isbonded via a metal-to-metal joint to the distal end of the pusher. Thepusher and coil are made of dissimilar metals. The coil-carrying pusheris advanced through the catheter to the site and a small electricalcurrent is passed through the pusher-coil assembly. The current causesthe joint between the pusher and the coil to be severed viaelectrolysis. The pusher may then be retracted leaving the detached coilat an exact position within the vessel. Since no significant mechanicalforce is applied to the coil during electrolytic detachment, highlyaccurate coil placement is readily achieved. In addition, the electriccurrent may facilitate thrombus formation at the coil site. The onlyperceived disadvantage of this method is that the electrolytic releaseof the coil may require a period of time that may inhibit rapiddetachment of the coil from the pusher.

Another method of placing an embolic coil is disclosed in U.S. Pat. No.5,108,407. This patent shows the use of a device in which embolic coilsare separated from the distal end of a catheter by the use ofheat-releasable adhesive bonds. The coil adheres to the therapeuticdevice via a mounting connection having a heat sensitive adhesive. Laserenergy is transferred through a fiber optic cable which terminates atthat connector. The connector becomes warm and releases the adhesivebond between the connector and the coil. Among the drawbacks of thissystem is that it involves generally complicated laser opticcomponentry.

There is a need to provide alternative mechanical mechanisms fordelivering implants, such as embolic coils, that combine accuratepositioning capability with rapid implant decoupling response times.

SUMMARY OF THE INVENTION

The present invention provides a mechanical occlusive implant deliveryassembly having a rapid response decoupling or detachment mechanism thatdoes not effect significant migration of the implant during release. Theassembly includes an occlusive implant device, such as an embolic coil,a pusher or device to carry the implant to the selected location, and anexpandable mechanism that is expanded or contracted to release theimplant at the selected site. The invention advantageously incorporatesa release mechanism that simply involves unloading a locking force,which is preferably uniformly applied, thereby avoiding the transmissionof any significant force to the implant during release. In addition, thelocking members preferably have generally, smooth, roundedconfigurations so that they do not catch and dislodge previouslypositioned coils upon retraction.

According to a first embodiment of the invention, the occlusive implantdelivery assembly includes an occlusive implant; a pusher having aproximal section and a distal section; a coupling having first andsecond portions, the first portion being coupled to the distal sectionof the pusher and the second portion being coupled to the implant; andan inflatable member having a proximal portion and a distal portion, theproximal portion being coupled to the distal section of the pusher. Atleast a portion of the inflatable member is disposed in the couplingsuch that when inflated, it expands the coupling and decouples thecoupling from either the implant or the pusher. With this arrangement,rapid implant release times can be achieved with minimal, if any, forcebeing applied to the implant. That is, the hydraulic pressure is onlytransmitted to the detachment point or juncture between the inflatablemember and the implant, and not to the implant.

According to another aspect of this embodiment, the inflatable memberand coupling are configured so that the hydraulic pressure generated bythe inflatable member is applied uniformly to the inner circumferentialsurface of the coupling. Thus, any force that may be applied to theimplant in the radial direction is countered by an equal, but oppositeforce, thereby avoiding implant displacement during release. In thepreferred embodiment, the coupling is cylindrical with an essentiallyuniform radius and the inflatable member is essentially symmetricalabout its longitudinal axis in the inflated and uninflated states.

According to another embodiment of the invention the implant deliveryassembly comprises an occlusive implant having a tubular portion; apusher having a proximal section and a distal section; and

-   -   an inflatable member having a first portion coupled to the        distal section of the pusher and a second portion disposed in        the tubular portion of the implant such that upon inflation of        the inflatable member the implant and member tend to separate.        More specifically, the coil slides off of the inflatable member.        In addition to causing minimal post delivery migration of the        implant, this construction provides an advantageously simple        one-piece decoupling mechanism, which can be readily        manufactured.

According to another aspect of this embodiment, the inflatable memberand tubular portion also are configured as described above so that thehydraulic pressure generated by the inflatable member is applieduniformly to the inner circumferential surface of the tubular portion.In the preferred embodiment, the inner surface of the tubular portion isessentially symmetrical about its longitudinal axis and the inflatablemember is essentially symmetrical about its longitudinal axis wheninflated or deflated to provide an essentially uniformly distributedforce to the inner circumference of the tubular section.

According to yet a further embodiment of the invention, the implantdelivery assembly comprises an occlusive implant having a tubularportion; a pusher having a proximal section and a distal section; a coremember slidably disposed within the pusher and extending into thetubular portion; and a locking member releasably coupled to the coil andcore member. With this construction the release mechanism is simplymechanically expanded to interlock the implant to the pusher and relaxedto release the implant.

In a first configuration, the locking member comprises an elastomericring, such as an O-ring, and the core member includes a locking portionand a tapered portion adjacent thereto. The diameter of the core memberexceeds the inner diameter of the ring such that when the ring ispositioned on the locking portion it expands and frictionally locks thetubular portion thereto. On the other hand, the tapered portion tapersto a diameter that allows the ring to contract. In the preferredembodiment, the tapered portion is less than or equal to the innerdiameter of the ring when the ring is in its relaxed state. When thecore member is retracted, the tapered portion becomes positioned withinthe ring and allows the ring to radially contract and release thetubular portion and, thus, the implant, as the locking member returns toits relaxed state.

In another configuration, the locking member comprises a flexible sleeveand the core member extends into the sleeve and is secured thereto. Thesleeve is configured so that when axially compressed, it expandsradially against the inner surface of the tubular portion andfrictionally locks the implant thereto. The core member is retracted tocompress the sleeve against a restraint, expand it radially and lock theimplant to the delivery assembly. When it is desired to release theimplant, the core member is advanced to remove the axial compression andradially contract the sleeve.

These configurations advantageously eliminate the need for auxiliaryhydraulics.

The above is a brief description of some of the features and advantagesof the present invention. Other features, advantages and embodiments ofthe invention will be apparent to those skilled in the art from thefollowing description, accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a catheter apparatus constructed according to a generalembodiment of the present invention;

FIG. 2 is an enlarged, fragmentary view of an occlusive implant deliveryassembly, constructed according to the principles of the presentinvention, disposed within a catheter;

FIG. 3 is a perspective view of the coupling mechanism that forms partof the release mechanism shown in FIG. 2;

FIG. 4 is an enlarged, fragmentary view of the implant delivery assemblyof FIG. 2 with the implant positioned at a desired location;

FIG. 5 is a further view of the implant delivery assembly shown in FIG.4 with the coupling of the release mechanism expanded to unlock andrelease the implant from the pusher;

FIG. 6 shows the release mechanism deflated and retracted from theimplant location;

FIG. 7 is an enlarged, fragmentary view of another embodiment of theimplant delivery system of the present invention with the releasemechanism in a locked state;

FIG. 8 illustrates the release mechanism of FIG. 7 in an unlocked state;

FIG. 9 is a further embodiment of the release mechanism of the presentinvention;

FIG. 10 is a further view of the release mechanism shown in FIG. 9showing the mechanism actuated to release the coil therefrom;

FIG. 11 is a further view of the release mechanism shown in FIGS. 8 and9 illustrating the implant fully detached from the mechanism;

FIG. 12 is an enlarged, fragmentary view of yet another embodiment ofthe release mechanism of the present invention showing the mechanism ina locked state;

FIG. 13 is a further view of the release mechanism of FIG. 12illustrating the mechanism in an unlocked configuration;

FIG. 14 is yet a further embodiment of the release mechanism of thepresent invention illustrating the mechanism in a locked configuration;and

FIG. 15 is a further view of the release mechanism of FIG. 14 showingthe mechanism in an unlocked configuration and the implant releasedtherefrom.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in detail, wherein like numerals indicate likeelements, several embodiments of an occlusive implant delivery assemblyare shown according to the principles of the present invention. Thevarious embodiments employ an expandable mechanism, which is expanded orcontracted, to decouple and release the implant at the desired site.Although variously configured implants can be used in conjunction withthe assembly of the present invention, an embolic coil type implant willbe described for purposes of example.

The operation of the assembly generally comprises the steps of (1)advancing a catheter through a vessel lumen, for example, to thevicinity of the site to be occluded (e.g., an aneurysm, vascularmalformation, or arterial venous fistula), (2) advancing the implantdelivery assembly through and beyond the catheter to the location, and(3) radially expanding or contracting the release mechanism to detachthe implant from the assembly.

Referring to FIG. 1, a catheter apparatus 2 suitable for guiding theocclusive implant delivery assembly and providing actuation pressure forthe hydraulically actuated release mechanism embodiments is shown.Catheter apparatus 2 generally includes a catheter 4, syringe 6 andsidearms (adapters) 8A and 8B. Catheter 4 generally comprises anelongate tubular member having proximal and distal end portions 10 and12. The catheter is preferably between about 50-300 cm in length, andtypically between about 60-200 cm in length. The catheter also isdesigned for accessing a vessel site at which, for example,vasoocclusion is desired. For example, the vessel site may be within asmall diameter vessel having 2-5 mm lumen diameter and accessible by wayof a tortuous vessel path which may involve sharp vessel turns andmultiple vessel branches. In that case, the catheter preferably has asmall diameter, flexible construction with a lumen diameter of less thanabout 40 mil, and preferably between about 8-30 mil. Catheters of thistype, which are typically used for accessing deep brain vascular sites,are commercially available.

The elongated tubular member or catheter 4 is secured at its proximalend 10 to sidearm 8A, which is of conventional design for introducingfluids or apparatus into the catheter. The end of proximal section 32 ofpusher 26, which will be described in more detail below, extends throughsidearm 8A and is coupled to the distal or downstream end of sidearm 8B.Sidearm 8B, which is otherwise essentially similar in construction tosidearm 8A, can include a tubular extension 14 that surrounds a portionof the pusher as shown in FIG. 1. Mandrel 54, 56 or 68, which extendsthrough the pusher, as will be discussed below in connection with FIGS.9-15, extends through one tube of sidearm 8B. The discharge tip ofsyringe 6, which is used in conjunction with the embodiments shown inFIGS. 2-11 is fluidly coupled to the other tube of sidearm 8B and, thus,the inner lumen of pusher 26 through which the aforementioned mandrelsextend.

Syringe 6 is of conventional construction and includes a cylindricalbarrel 18 and a plunger 20 that is reciprocally mounted therein. Astopcock 22 preferably is provided in the discharge piece of the syringefor opening or closing the fluid connection between the syringe andpusher lumen. Alternatively, the stopcock can be provided in a connector(not shown) that couples the discharge piece of the syringe to sidearm8B. When the stopcock is in the closed position, the decoupling orrelease mechanism of the implant delivery assembly will not beinadvertently actuated, thereby avoiding wrongly positioning the implantwithin the body as a result of such accidental discharge of liquid fromthe syringe into the catheter.

As discussed above, the implant delivery assembly, which is generallydesignated with reference numeral 24 in FIG. 1, is guided throughcatheter 4 towards the intended vasoocclusion site. Occlusive implantdelivery assembly 24 generally comprises a pusher or elongated carriermember 26, a coil type occlusive implant 28 and a decoupling or releasemechanism for releasing the implant from the assembly. Although coil 28is shown in the drawings as a uniform diameter helical coil wire, it mayhave other configurations. It is important, however, that the coil bedimensioned to be able to be advanced through a catheter that is sizedto access the desired site. The coil may be made of radiopaque,biocompatible metal such as platinum, gold, tungsten, stainless steel oralloys of these metals. Preferably, the coil comprises platinum, gold,tungsten or alloys of these metals so that its location at the site maybe readily viewed radiographically.

For use in occluding peripheral or neural sites, the coils willtypically be made of 0.05 to 0.15 mm diameter platinum wire that iswound to have an inner diameter of 0.15 to 0.96 mm with a minimum pitch(i.e., the windings are close or tight). The length of the wound wire(i.e., the coil) will normally be in the range of 0.5 to 60 cm, andpreferably 0.5 to 40 cm. For wires intended for use in vessels withdiameters of about 2 mm and smaller, the coil has a preferred length ofabout 0.5 to 20 cm. The coil can have any shape. For example, it can beformed so that it takes an essentially linear configuration in which itmay be advanced through the catheter and assume a randomly orientedconfiguration, such as helical, after it is released from the catheterand in a relaxed state as disclosed in U.S. Pat. No. 4,994,069, which ishereby incorporated herein by reference.

Referring to FIGS. 2-6, a first embodiment of the occlusive implantdelivery assembly, will be described. The delivery assembly shown inFIGS. 2-6 generally comprises a pusher or elongated carrier member 26,coil 28 and coupling 30. The pusher preferably has a tubularconstruction to provide a lumen for fluidly coupling a source ofpressurized fluid, such as syringe 6, and an inflatable member utilizedin decoupling the coil from the pusher, as will be described in moredetail below. Pusher 26 also preferably has a proximal section that isrigid enough to facilitate torque transmission to the distal portion ofthe pusher. The distal section of the pusher may be constructed to bemore flexible than the proximal portion to facilitate navigation of thedistal section into very tiny vessels encountered in the brain, forexample.

In the preferred embodiment, proximal tubular section of pusher 26(designated with reference numeral 32) is a metal tube, preferably astainless steel tube, and the distal section of pusher 26, section 34,comprises a coil 36, which is wrapped in a flexible, elastomeric film 38to fluidly seal the spaces between the coil windings. Film 38 alsooverlaps section 34 to seal the juncture between section 34 an coil 36.Film 38 can be in the form of shrinkwrap and, thus, applied to coil 36and proximal section 34 with conventional shrinkwrap techniques. Coil 36and, thus, distal coiled section 34 is secured to the proximal tubularsection 32 by welding, soldering, brazing, or adhesive.

Alternatively, a more simple pusher configuration may be used in whichthe pusher comprises a rigid plastic tube which can be ground with atapered distal section to achieve the desired flexibility. Suitablematerials for this configuration include PEEK and polyimide. The innerdiameter of the distal section in this configuration preferably issignificantly less than the outer diameter of the proximal section towhich the balloon can attached (e.g., glued). In a preferred embodiment,the lumen, which provides for fluid flow between the source ofpressurized fluid and the balloon, has a diameter of about 0.007 inchthroughout its length and the distal section has an outer diameter ofabout 0.014 inch. The outer diameter of the proximal section depends onthe application. For a 3 French catheter, the outer diameter of theproximal section may be about 0.016 to 0.018 inch. Although particularpusher configurations have been described, it should be understood thatother configurations may be used without departing from the scope of theinvention.

A conventional inflatable balloon 40, having a construction similar tothose used in conventional balloon catheters, is secured to the distalend of coil 36 by adhesive, for example, such that a fluid tight path isformed between the interior of the balloon and the central lumen ofpusher 26, which is formed by proximal and distal sections 32, 34 ofpusher 26.

Returning to FIG. 2, balloon 40 extends into tube 42, which is alsosecured to implant coil 28 by welding, soldering, brazing or adhesive.As shown in FIG. 2, coupling 30 comprises a tubular member or split tubehaving slots formed in the axial direction and which open into the endof the tube that is directly coupled to the distal portion of pushercoil 38. The tube to pusher coupling can be accomplished by a pressurefit, welding, soldering, brazing or adhesive. Slots 42 form multiplesegments 44 in tubular coupling 30 and facilitate displacement of thosesegments to effect release of the coil implant from the pusher, as willbe described in more detail below. Although a two slot configuration isshown, other multiples of slots can be used to facilitate displacementof the proximal portion of the coupling as well as other conventionaljaw or latch clamping configurations.

Tubular coupling 30 can be made from platinum, stainless steel orplastic that is biocompatible with the environment in which the couplingwill be placed. The coupling 30 preferably also has a very thin wall ofabout 0.001 to 0.0003 inches.

The implant delivery assembly of FIGS. 2-6 will be further described byway of the following operative example which is provided merely forexemplary purposes and is not intended to limit the invention to aparticular application.

A catheter is inserted through the vessel lumen to the site to beoccluded (e.g., an aneurysm, vascular malformation, or arteriovenousfistula. Conventional catheter insertion and navigational proceduresinvolving guidewire and/or flow-directed means may be used to access thesite with the catheter. Thus, although not shown, catheter 4 may includea guidewire useable therewith to guide the distal end of the cathetertoward the desired or selected occlusion site. Guidewires of this typeare commercially available, and generally include an elongate wirehaving a tapered, wire-wound distal end region which is adapted to beadvanced through a tortuous vessel path, with the catheter being movedaxially along the advanced guidewire.

Once the distal end of the catheter is positioned at the selected site(its location may be determined by a coating at the distal end of thecatheter with a radiopaque material or otherwise affixing such amaterial to the distal end of the catheter or incorporating such amaterial into the distal end of the catheter), the catheter is cleared.For example, if a guidewire has been used to position the catheter, itis withdrawn from within the catheter.

Then, the implant delivery assembly, as shown in FIG. 2, is introducedinto the proximal end portion of catheter 4, and advanced toward thedistal end portion of catheter 4. The proximal end of pusher 26 ismanipulated via sidearm 8B, to which it is attached, so that coupling 30and coil implant 28 extend beyond the distal end of the catheter withcoupling 30 free of the catheter and the coil positioned exactly at thedesired site (FIG. 4). Stopcock 22 is then placed in an open positionand the plunger of syringe 6 advanced to inflate balloon 40 as shown inFIG. 5. As balloon 40 is inflated, it further opens split tube orcoupling 30, i.e., segments 44 are displaced radially outward todecouple coupling 30 and coil 28 from pusher 26 without transmitting anysignificant force to coil 28. The balloon is then deflated by retractingthe plunger in syringe 6, thereby releasing coupling 30 from balloon 40so that the pusher can be retracted without altering the position ofcoil 28. After the desired number of coils have been placed at the site,the catheter is withdrawn from the vessel.

Referring to FIGS. 7 and 8, a further embodiment of the release ordecoupling mechanism is shown similar to that shown in FIGS. 2-6, but inwhich coupling 30′ has its proximal portion fixedly secured to thedistal end of coiled portion 34. In addition, coupling 30′ includes endwalls 48 at its distal end for overlapping end piece or cap 50 providedat the proximal end of coil implant 28′. That is the end walls, whichgenerally form jaws, releasably secure coil 28′ to coupling 30′ and,thus, releasably secure coil 28′ to pusher 26. Coupling 30′ also differsfrom coupling 30 in that slots 42′ are formed in the distal portion ofthe coupling. Once the coil implant is positioned at the desiredlocation, fluid is introduced through the hollow pusher member and intoballoon 40, as described above, to displace segments 44′ radiallyoutward and release coil 28′ from coupling 30′ (FIG. 8). The balloon canthen be deflated and the pusher retracted. With this configuration, thecoupling is advantageously withdrawn with the pusher.

Referring to FIGS. 9-11, a further embodiment of the invention is shown.This embodiment essentially differs from those described above in thatthe release or decoupling mechanism simply comprises a balloon. Theballoon extends from the pusher with its proximal portion close fitwithin coil 28. When it is desired to deploy the coil, the balloon isinflated, and as the balloon expands, the coil slides off the end of theballoon as will be described in more detail below.

The decoupling mechanism of FIGS. 9-11 comprises a balloon 40′ havingits open end secured to the distal coiled section 34 of pusher 26, forexample, by adhesive. Balloon 40′ is packed into the proximal portion ofcoil 28 such that the balloon frictionally engages the inner surface ofcoil 28 and secures the coil to the balloon. To enhance the securementbetween the coil and balloon, the balloon is constructed such that, whenin the deflated state, the balloon has a plurality of circumferentiallyextending ribs 52, which preferably are configured to have a pitchcorresponding to that of the coil so that the ribs can snugly fitbetween the windings of the coil. The ribs can be formed by placing amandrel into the balloon, wrapping a thread around the balloon in theregions where the ribs are desired to be located, and then dipping theballoon, mandrel and thread assembly in a reservoir of elastomericmaterial, such as silicon, to form an outer ribbed elastomeric coatingfor the balloon.

The decoupling mechanism of the embodiment illustrated in FIGS. 9-11also preferably includes a mandrel 54 which extends from outside sidearm8B through catheter 12 via the interior lumen of pusher 26 and intoballoon 40′. Mandrel 52 facilitates inserting balloon 40′ within coil 28and preferably is sized to force the outer wall of the balloon againstthe inner circumferential surface of coil 28 to enhance the interlockingconnection between the coil and balloon.

In operation, the pusher and the mandrel are advanced through catheter 4until coil 28 is positioned at the desired location (FIG. 9). Themandrel is then retracted or withdrawn from the balloon and the syringeactuated to inflate the balloon 40′ as described above (FIG. 10). Inthis case, it is important that mandrel 54 is sized so that when placedin the pusher lumen, sufficient space between the mandrel and the innersurface of the proximal and distal sections 32, 34 of pusher 26 isformed. In this manner, the interior of balloon 40′ can be fluidlycoupled to the syringe 6 when stopcock 22 is in the open position andthe mandrel is in the pusher. As the balloon inflates and stretches, theribs generally flatten and the proximal end of coil 28 slides off thedistal end portion of balloon 40′. In order to avoid axial displacementof the coil, the balloon can be retracted as it is inflated.Alternatively, the end of the balloon can be positioned where theproximal end of the coil is desired to be finally located. As theballoon inflates, the proximal end of the coil will ultimately belocated at the distal end of the balloon. The balloon position can bedetermined by conventional means such as radiographic techniques. Thepusher can then be retracted as shown in FIG. 11 and the balloondeflated. The procedure is repeated if the delivery of additional coilsis desired.

Referring to FIGS. 12-15, further embodiments of the invention are shownin which the release or decoupling mechanism comprises a mechanicallyexpandable or locking member rather than a fluidly inflatable/expandableballoon. The expandable locking member fits within the proximal end ofthe coil and is radially expanded to grip the inner circumferentialsurface of the coil. When the expandable member is returned to agenerally relaxed state so that its diameter decreases, the coil isreleased.

The decoupling mechanism shown in FIGS. 12 and 13 generally comprisescore wire or actuating member 56 and an elastomeric ring or lockingmember 60, such as an O-ring, which is slidably mounted on core wire 56.Core wire or mandrel 56 includes a proximal locking portion 62, whichpreferably has a generally uniform diameter, and a distal tapered orunlocking portion. More specifically, the diameter of the core wirelocking portion exceeds the inner diameter of the ring such that whenthe ring is positioned on the locking portion it expands against theinner circumferential surface of coil 28 and frictionally locks the coilthereto (FIG. 12). On the other hand, the tapered portion tapers to adiameter that allows the ring to radially contract and release the coil.In the preferred embodiment, the tapered portion tapers to a diameterthat is less than or equal to the inner diameter of the ring when thering is in its relaxed state. When the core wire is retracted, thetapered portion becomes positioned within the ring and allows the ringto radially contract and release the coil as it returns to its relaxedstate (FIG. 13). Core wire 56 can be ground to the desired shape as isconventional in the art.

In addition, the distal portion of actuating member 56 includes a stopmember 66 to ensure that the elastomeric ring 60 does not becomedetached from the actuating member. Otherwise the ring would become freeto migrate in the blood stream, which could result in an embolism. Adisc 58 optionally may be secured to the distal end of coil 36 bywelding, soldering, brazing or adhesive to simplify retraction of thepusher as will be discussed in more detail below.

In operation, ring 60 is positioned on the locking portion of core wire56 between the core wire and coil 28. Then, the pusher and core wire areboth advanced through catheter 4 so that coil 28 eventually extendsbeyond the catheter and is positioned at the desired location (FIG. 12).Once coil 28 is so positioned, core wire 56 is slowly retracted, causingthe tapered distal portion 54 to slide within the opening of ring 60,thereby allowing the ring to return to its relaxed, unexpanded state. Inthis state, the ring diameter is significantly less than the innerdiameter of coil 28 to facilitate rapid coil release. As the core wireis further retracted, stop member 66, which has a larger diameter thanthe inner diameter of ring 60, catches the ring and carries it as thecore wire is completely withdrawn from coil 28 (FIG. 13). When disc 58is incorporated, the entire pusher 26 can be withdrawn by merelyretracting actuating member 56 as stop member 66 acts on coil 36 throughring 60 and disc 58 as is apparent from the drawings.

Referring to FIGS. 14 and 15, a further embodiment of the release ordecoupling mechanism is shown. The decoupling mechanism illustrated inthese figures generally comprises a core wire or actuating member 68,disc or retaining member 70 and sleeve or locking member 72. Sleeve 72is compressed to expand it in the radial direction and interlock thecoil to the pusher assembly (FIG. 14). Once in place, it is extended torelease the coil therefrom (FIG. 15).

Core wire 68 extends from sidearm 8B as shown in FIG. 1. The distal endportion of core wire 68, preferably is secured to the distal end ofsleeve 72 so that when the core wire 68 is retracted, sleeve 72 iscompressed in the axial direction against disc 70 as shown in FIG. 14.Sleeve 72 preferably is of a material that, upon compression in theaxial direction, will expand radially to interlock with coil 28.Accordingly, sleeve 72 can comprise fabric and, preferably, comprisesbraided material in which the degree of radial expansion generallydepends upon the pitch of the braiding.

The actuator is initially positioned as shown in FIG. 14 with the openend of sleeve 72 compressed against disc 70. The coil is released fromthe pusher assembly by simply advancing the core wire 68 as shown inFIG. 15 while maintaining pusher 26 is a fixed position. Then, pusher 26and core wire 68 are concurrently retracted so as to maintain sleeve 72in its extended position, while withdrawing sleeve 72 from coil 28without placing any significant mechanical force on the coil in eitherthe radial or axial direction.

The above is a detailed description of several embodiments of theinvention. It is recognized that departures from the disclosedembodiments may be made within the scope of the invention and thatobvious modifications will occur to a person skilled in the art. Thefull scope of the invention is set out in the claims that follow andtheir equivalents. Accordingly, the claims and specification should notbe construed to unduly narrow the full scope of protection to which theinvention is entitled.

1. A method for detaching an occlusive coil at a site to be occluded ina body, comprising: i) providing a catheter having a distal end and anocclusive coil attached to the distal end such that a distal end of thecoil is distal to the catheter distal end; ii) inserting the catheter ina body such that the coil is placed at a site to be occluded; iii)directing a fluid to the catheter distal end through a lumen in saidcatheter such that the fluid radially expands the catheter distal end tothereby release said coil from the distal end of the catheter.
 2. Themethod of claim 1, wherein said catheter is a tube.
 3. The method ofclaim 1, wherein the catheter distal end further comprises a radiallyexpanding coupling that releases the coil when the coupling is radiallyexpanded by fluid pressure.
 4. The method of claim 1, wherein the coilis not in fluid communication with the lumen.
 5. A system for deliveringan occlusive coil to a vascular passage, comprising: an occlusive coilhaving a distal end; and a delivery member having a coupling portion,the coupling portion having a distal end that is proximal to the distalend of the occlusive coil, the coupling portion changing configurationin response to fluid pressure applied to the coupling portion to releasethe occlusive coil from the coupling portion.
 6. The system of claim 5,wherein the coupling portion changes configuration by expanding in asubstantially radial direction in response to fluid pressure applied tothe coupling portion.
 7. The system of claim 5, wherein the couplingportion comprises a coupling member that couples to the occlusive coilby clamping the occlusive coil in a substantially fixed position, thecoupling member changing configuration by expanding in a substantiallyradial direction in response to fluid pressure applied to the couplingmember.
 8. The system of claim 7, wherein the coupling member comprisesa plurality of slots that engage the implant.
 9. The system of claim 5,wherein the coupling portion is configured so that the occlusive coil isnot in fluid communication with the coupling portion.
 10. The system ofclaim 5, wherein the coupling portion comprises a distal portion of thedelivery member.
 11. A system for delivering an occlusive coil to avascular passage, comprising: an occlusive coil having a distal end; anda delivery member, the delivering member comprising a deformablecoupling portion that changes shape in response to fluid pressureapplied to the coupling portion to release the occlusive coil from thecoupling portion, the coupling portion having a distal end that isproximal to the distal end of the occlusive coil.
 12. The system ofclaim 11, wherein the coupling portion changes shape by expandingsubstantially radially outward in response to fluid pressure applied tothe coupling portion.
 13. The system of claim 11, wherein the couplingportion comprises a coupling member that, when in one shape, isconfigured to couple the occlusive coil to the coupling member.
 14. Thesystem of claim 13, wherein the coupling member couples the occlusivecoil by clamping action.
 15. The system of claim 11, wherein thecoupling portion is configured so that the occlusive coil is not influid communication with the coupling portion.
 16. The system of claim11, wherein the coupling portion comprises a distal portion of thedelivery member.